This double bill of Alan Bennett bio-plays has transferred to the Duchess Theatre (meaning the National now has four productions running concurrently in the West End), affording an opportunity for those who missed it on the South Bank to catch Alex Jennings' superlative performance as the reluctant national treasure.

The first playlet is the poetic 30-minute Hymn, performed by Jennings and a string quartet. Written - and first performed - by Bennett in collaboration with composer George Fenton, the 2001 piece is a meditation on memory, music and, centrally, the playwright's relationship with his Dad, a bass-playing Leeds butcher.

Infused with Bennett's trademark observations (sitting behind the bass section at a concert is compared to "watching a circus from behind the elephants"), it doesn't quite hit the emotional heights to come in the second half but a stirring climax neatly nods to Larkin.

Jennings affectionately inhabits his subject without ever slipping into Spitting Image territory. Bennett's soft Yorkshire lilt is so often imitated that it can difficult to listen past the voice to hear the words, but Jennings makes it easy. He skilfully plays with the quartet like a fifth instrument, at times involving the musicians directly to demonstrate his stuttering early attempts as a would-be violinist.

The second piece, Cocktail Sticks, is such an ideal companion of the first that it's difficult to imagine they were ever not a pair - and that they're staged by different directors (Nadia Fall and Nicholas Hytner, respectively). More formal in structure than its predecessor, it includes Bennett's parents and other peripheral characters to show how the writer grew to appreciate his "very ordinary" childhood.

He poignantly, and humorously, deals with the fall-out of his mother's mental decline. When first diagnosed with depression she refuses to accept it, believing the illness belongs to "the better class", but after her husband's death it becomes more acute and eventually leads to an achingly familiar end.

Jeff Rawle and Gabrielle Lloyd give accomplished performances as Mr and Mrs B, ably supported by Derek Hutchinson and Sue Wallace as myriad supporting players (most hysterically the nouveau riche parents of one of Alan's university friends). But once again it's Jennings who shines brightest with his pitch-perfect portrayal of the blazer-wearing, squarely-bespeckled scribe.

This is an evening to savour, for Bennett fans old and new. And how sad it is that his journey from working class boy to literary giant still seems so remarkable in light of the continued domination of the privately-educated in public life.